/**
 * Author: Koh Zi Han, based on implementation by Koh Zi Chun
 */
CodeMirror.defineMode("scheme", function (config, mode) {
  var BUILTIN = "builtin", COMMENT = "comment", STRING = "string",
    ATOM = "atom", NUMBER = "number", BRACKET = "bracket", KEYWORD = "keyword";
  var INDENT_WORD_SKIP = 2, KEYWORDS_SKIP = 1;

  function makeKeywords(str) {
    var obj = {}, words = str.split(" ");
    for (var i = 0; i < words.length; ++i) obj[words[i]] = true;
    return obj;
  }

  var keywords = makeKeywords("λ case-lambda call/cc class define-class exit-handler field import inherit init-field interface let*-values let-values let/ec mixin opt-lambda override protect provide public rename require require-for-syntax syntax syntax-case syntax-error unit/sig unless when with-syntax and begin call-with-current-continuation call-with-input-file call-with-output-file case cond define define-syntax delay do dynamic-wind else for-each if lambda let let* let-syntax letrec letrec-syntax map or syntax-rules abs acos angle append apply asin assoc assq assv atan boolean? caar cadr call-with-input-file call-with-output-file call-with-values car cdddar cddddr cdr ceiling char->integer char-alphabetic? char-ci<=? char-ci<? char-ci=? char-ci>=? char-ci>? char-downcase char-lower-case? char-numeric? char-ready? char-upcase char-upper-case? char-whitespace? char<=? char<? char=? char>=? char>? char? close-input-port close-output-port complex? cons cos current-input-port current-output-port denominator display eof-object? eq? equal? eqv? eval even? exact->inexact exact? exp expt #f floor force gcd imag-part inexact->exact inexact? input-port? integer->char integer? interaction-environment lcm length list list->string list->vector list-ref list-tail list? load log magnitude make-polar make-rectangular make-string make-vector max member memq memv min modulo negative? newline not null-environment null? number->string number? numerator odd? open-input-file open-output-file output-port? pair? peek-char port? positive? procedure? quasiquote quote quotient rational? rationalize read read-char real-part real? remainder reverse round scheme-report-environment set! set-car! set-cdr! sin sqrt string string->list string->number string->symbol string-append string-ci<=? string-ci<? string-ci=? string-ci>=? string-ci>? string-copy string-fill! string-length string-ref string-set! string<=? string<? string=? string>=? string>? string? substring symbol->string symbol? #t tan transcript-off transcript-on truncate values vector vector->list vector-fill! vector-length vector-ref vector-set! with-input-from-file with-output-to-file write write-char zero?");
  var indentKeys = makeKeywords("define let letrec let* lambda");


  function stateStack(indent, type, prev) { // represents a state stack object
    this.indent = indent;
    this.type = type;
    this.prev = prev;
  }

  function pushStack(state, indent, type) {
    state.indentStack = new stateStack(indent, type, state.indentStack);
  }

  function popStack(state) {
    state.indentStack = state.indentStack.prev;
  }

  /**
   * Scheme numbers are complicated unfortunately.
   * Checks if we're looking at a number, which might be possibly a fraction.
   * Also checks that it is not part of a longer identifier. Returns true/false accordingly.
   */
  function isNumber(ch, stream) {
    if (/[0-9]/.exec(ch) != null) {
      stream.eatWhile(/[0-9]/);
      stream.eat(/\//);
      stream.eatWhile(/[0-9]/);
      if (stream.eol() || !(/[a-zA-Z\-\_\/]/.exec(stream.peek()))) return true;
      stream.backUp(stream.current().length - 1); // undo all the eating
    }
    return false;
  }

  return {
    startState:function () {
      return {
        indentStack:null,
        indentation:0,
        mode:false,
        sExprComment:false
      };
    },

    token:function (stream, state) {
      if (state.indentStack == null && stream.sol()) {
        // update indentation, but only if indentStack is empty
        state.indentation = stream.indentation();
      }

      // skip spaces
      if (stream.eatSpace()) {
        return null;
      }
      var returnType = null;

      switch (state.mode) {
        case "string": // multi-line string parsing mode
          var next, escaped = false;
          while ((next = stream.next()) != null) {
            if (next == "\"" && !escaped) {

              state.mode = false;
              break;
            }
            escaped = !escaped && next == "\\";
          }
          returnType = STRING; // continue on in scheme-string mode
          break;
        case "comment": // comment parsing mode
          var next, maybeEnd = false;
          while ((next = stream.next()) != null) {
            if (next == "#" && maybeEnd) {

              state.mode = false;
              break;
            }
            maybeEnd = (next == "|");
          }
          returnType = COMMENT;
          break;
        case "s-expr-comment": // s-expr commenting mode
          state.mode = false;
          if (stream.peek() == "(" || stream.peek() == "[") {
            // actually start scheme s-expr commenting mode
            state.sExprComment = 0;
          } else {
            // if not we just comment the entire of the next token
            stream.eatWhile(/[^/s]/); // eat non spaces
            returnType = COMMENT;
            break;
          }
        default: // default parsing mode
          var ch = stream.next();

          if (ch == "\"") {
            state.mode = "string";
            returnType = STRING;

          } else if (ch == "'") {
            returnType = ATOM;
          } else if (ch == '#') {
            if (stream.eat("|")) {          // Multi-line comment
              state.mode = "comment"; // toggle to comment mode
              returnType = COMMENT;
            } else if (stream.eat(/[tf]/)) {      // #t/#f (atom)
              returnType = ATOM;
            } else if (stream.eat(';')) {        // S-Expr comment
              state.mode = "s-expr-comment";
              returnType = COMMENT;
            }

          } else if (ch == ";") { // comment
            stream.skipToEnd(); // rest of the line is a comment
            returnType = COMMENT;
          } else if (ch == "-") {

            if (!isNaN(parseInt(stream.peek()))) {
              stream.eatWhile(/[\/0-9]/);
              returnType = NUMBER;
            } else {
              returnType = null;
            }
          } else if (isNumber(ch, stream)) {
            returnType = NUMBER;
          } else if (ch == "(" || ch == "[") {
            var keyWord = '';
            var indentTemp = stream.column();
            /**
             Either
             (indent-word ..
             (non-indent-word ..
             (;something else, bracket, etc.
             */

            while ((letter = stream.eat(/[^\s\(\[\;\)\]]/)) != null) {
              keyWord += letter;
            }

            if (keyWord.length > 0 && indentKeys.propertyIsEnumerable(keyWord)) { // indent-word

              pushStack(state, indentTemp + INDENT_WORD_SKIP, ch);
            } else { // non-indent word
              // we continue eating the spaces
              stream.eatSpace();
              if (stream.eol() || stream.peek() == ";") {
                // nothing significant after
                // we restart indentation 1 space after
                pushStack(state, indentTemp + 1, ch);
              } else {
                pushStack(state, indentTemp + stream.current().length, ch); // else we match
              }
            }
            stream.backUp(stream.current().length - 1); // undo all the eating

            if (typeof state.sExprComment == "number") state.sExprComment++;

            returnType = BRACKET;
          } else if (ch == ")" || ch == "]") {
            returnType = BRACKET;
            if (state.indentStack != null && state.indentStack.type == (ch == ")" ? "(" : "[")) {
              popStack(state);

              if (typeof state.sExprComment == "number") {
                if (--state.sExprComment == 0) {
                  returnType = COMMENT; // final closing bracket
                  state.sExprComment = false; // turn off s-expr commenting mode
                }
              }
            }
          } else {
            stream.eatWhile(/[\w\$_\-]/);

            if (keywords && keywords.propertyIsEnumerable(stream.current())) {
              returnType = BUILTIN;
            } else returnType = null;
          }
      }
      return (typeof state.sExprComment == "number") ? COMMENT : returnType;
    },

    indent:function (state, textAfter) {
      if (state.indentStack == null) return state.indentation;
      return state.indentStack.indent;
    }
  };
});

CodeMirror.defineMIME("text/x-scheme", "scheme");